Continuous flow system for the determination of trace vanadium in natural waters utilizing in-line preconcentration/separation coupled with catalytic photometric detection

Abstract

A sensitive and rapid method is presented for the determination of vanadium at ng to sub-ng ml −1 levels in natural waters, in which in-line preconcentration/separation is directly coupled with catalytic detection of vanadium in a flow-injection system. Vanadium was adsorbed on a small column packed with Sephadex G-25 gel and desorbed with a small volume of 0.010 M HCl. The catalytic action of vanadium on the oxidation of chromotropic acid (1,8-dihydroxy-3,6-naphthalenedisulphonic acid) by bromate in pH 3.8 buffered media was used in the sensitive determination of vanadium. Effective preconcentration/separation of trace vanadium can be achieved from Fe(III), Cu(II) and a large excess of sodium chloride in seawater sample. A linear calibration using a 5 m sample loop was obtained for vanadium in the range 0–2.5 ng ml −1. The limit of detection was 0.02 ng ml −1 and the relative standard deviation was 1.2% for 1.0 ng ml −1 vanadium ( n=5). The present FIA system is rapid and sensitive and can be readily applied to river water and coastal seawater samples.